Double-walled electric incandescent lamp



Feb. 6, 1940. E. GOMON ET DOUBLE-WALLED ELECTRIC INCANDESCENT LAMP Filed Jan. 14, 1939 Patented Feb. 6, 1940 I r g 2,133,945

UNITED STATES PATENT OFFIC DOUBLE-WALLED ELECTRIC INCANDESCENT LAMP Edouard Gomonet, Paris, France, asslgnor to Soclete Anonyme pour les Applications dc lElectrlcit et des Ga: Bares, Etablissements Claude-Pu et Silva, Paris, France Application January 14, 1939, Serial No. 250,902 In Switzerland January 28, 1938 8 Claims. (CL 176-16) It is known to make incandescent, electric, The liquid adapted must be transparent to the lamp bulbs with a double well. With such lamps useful rays emitted by the filament, it must not it is often found that the outer bulb becomes exattack the walls of the two bulbs and must not cessively hot especially if the volume of the inner freeze too easily- Further. t must t produce,

bulb is relatively small. In order to avoid this under the action of the prolonged heating to drawback it is known to fill the outer bulk with which it is exposed during working, a quantity a gas having a greater heat conductivity than of volatile decomposition products which would air or to cause a liquid to circulate between the dangerously increase the internal pressure in the two bulbs. bulb, nor form coloured products which would 10 The first method however, is foundto be inintercept the li ht- 10 suliiciently effective if it is desired to use inner Good results are obtained when using saturbulbs of very small volume, while the second ated hydrocarbons or mixtures of such hydronecessitates the use of bulky and complicated carbons, such as Vaseline oil. This liquid may not apparatus. A liquid must be used which leaves at first sight appear very suitable owing to its no deposit, for example distilled'water, and a low heat conductivity. In use it has, however, 15 small pump must be provided for ensuring cirbeen found very satisfactory owing to its high culation of this water between the lamp and a .co-eflicient of expansion which results in large cooling device. convection currents thus facilitating boiling in The chief object of the invention is to obtain the upper portion of the liquid.

very efficient cooling of the inner bulb by simple In order to obtain completely even boiling, a. 20

and automatic means. porous substance for initiating the-formation of This object is attained according to the invengas bubbles may be provided near the top of tion by providing between the two walls a liquid the liquid. Further, the convection currents may in which the inner bulb is immersed, and which be assisted by suitably located partitions.

only partly fills the space between the two walls, Vaseline oil has the further advantage of be- 2.5 the said liquid boiling during the operation of ing sufilciently transparent to infra-red rays. the lamp and the emitted vapours condensing which is very advantageous for lamps'for genupon the part of the outer bulb which is above eral lighting where it is of advantage not to the level of the liquid. retain in the lighting apparatus, the heat due When such a lamp is put in operation the iilato the radiated energy. 30 ment transmits heat to the wall of the lntemal 0n the contrary, in certain cases the infra-red bulb which becomes heated and in turn transenergy emitted produces injurious overheating. mits the heat received to the liquid. The hotter Thus, f r xample, in lamps used in cinematothis liquid becomes, the greater the increase in its r phic projectors the infra-red rays abnorm y vapour pressure. The vapours emitted condense heat the Condenser lens f the ppar us and 35 upon the wall of the external bulb which is cooled al th fun A rdin t a further feature by the surrounding air. As the pressure con" of the invention use is in such cases made of tinues to rise, the heat transmission from the a liq d a s n t i ad. fo example inner to the outer bulb increases, The nature of water to which has been added a few thousandth the liquid and the dimensions of the external parts of copper sulphate This iquid t ansmits bulb must be so chosen that under ordinary t e ma o portion of t e energy t the uppe working conditions the temperature of the inner P o the Outer bulb and e light r ys emer bulb is sufliciently low to prevent the liberation c from the lamp will contain Practically 110thof a gas from said bulb which would attack the beyond the useful ay filament, and that the vapour pressure inside the In the same way a. coloured liquid. may be outer bulb does not become such as to cause it used f correcting the light e itted by the t b r t, 4 filament so as to obtain a whiter light or a col- In order to facilitate the difljusion of the vapour cured e Use can also be a e of a luminesfrom the surface of the liquid to the walls which cent liquid- The unused y a-V olet) will act as condensers, it is advisable not to leave in e absorbed by h q d and transformed into 50 the outer bulb too high a pressure of non-con- Visible reysdensable gas. However, too high a vacuum should The upp portion of t Outer bulb ay be 0 not be created if boiling of the liquid accomshaped and can be of such a. nature as to facilipanied by violent sudden jerks therein are to tate the heat exchange. For examplelntlre case be avoided. of projection lamps in which the upward light 5 rays are not used, the upper portion of the outer bulb could be made oi metal. This metal part can carry any known cooling means (fins, tubular shaves, etc.). This cooling can be accelerated by means of a current of air or water circulation.

If the lamps according to the present invention were put in operation in an over heated apparatus, the pressure in the outer bulb might rise abnormally. This risk is avoided by providing a fuse which interrupts the current when the temperature of the liquid becomes excessive.

For certain lamps, for example, projection lamps the luminous flux must be directed. The two bulbs can then be so shaped that the liquid between them constitutes the first element or an optical projection system intended to direct the light.

For high power lamps the outer bulb can be made detachable so that in case of the filament breaking only the inner bulb need be replaced.

Figures 1, 2 and 3 of the accompanying drawing show diagrammatically and by way of example two embodiments of the invention.

Figure 1 represents a xenon-and. nitrogen-filled incandescent lamp bulb having a double coiled tungsten filament. The inner bulb i is immersed in Vaseline oil. After this oil has been placed in the outer bulb E the latter is filled with nitrogen at a pressure of l centimetre of mercury. During working the oil vapours condense upon the wall of the outer bulb E. The fuse i1 is a guard against excessive heating. The fuse is melts on the occurrence of an excess voltage due to arcing.

Figures 2' and 3 represent a projection lamp according to the invention. As shown in Figure 3 which is a section on the line elf-b Figure 2 the two bulbs are so shaped that a large portion of the light is concentrated upon the condenser lens of the projection apparatus.

The ring of porous substance P ensures regular boiling in the upper part of the liquid. The lower part of the outer bulb E is of glass up to the line S, and the upper part is of metal. This metal carries the fins L. According to circumstances these fins can be enclosed in the projector so as to give them the benefit of the air current from the fan which is normally provided in many projectors or they can be placed in a region above the normal height of the projector in order to liberate the heat outside the apparatus.

I claim:

1. A double-walled electric incandescent lamp having a liquid which only partly fills the space between the two walls, the inner bulb being im-.

mersed in the said liquid which during operation of the lamp, boils and emits vapours which condense upon the part of the outer bulb which is above the level of the liquid.

2. A lamp according to claim 1, wherein vaseline oil is used as the liquid between the two bulbs.

3. A lamp according toclaim 1, wherein a liquid is used which absorbs the undesired rays.

4. A. lamp according to claim 1, wherein a luminescent liquid is used.

5. A lamp according to claim 1, wherein the two bulbs are so arranged relatively to each other that the liquid constitutes an optical element for distributing the rays emitted.

' 6. A lamp according to claim 1 provided with a fuse which is adapted to interrupt the current if the temperature of the liquid becomes too high.

' cane GOMO. 

